The European Commission has "drawn up a calendar according to which France and Italy are due to present additional measures", Merkel told newspaper Die Welt in an interview.
"That's justified because both countries are in the process of carrying out reforms," she said.
"But the Commission has also said in a clear manner that what is on the table to date is still insufficient. That's something that I agree with," she said, according to extracts released in advance by the newspaper.
Last month, the EU gave France — along with fellow deficit laggards Italy and Belgium — an extra three months to fix their budgets but warned they would still incur penalties if they failed to curb spending.
The European Commission, the EU's executive arm, singled out France for special criticism, saying it had made "limited progress" in reducing fiscal red ink.
France is set for a deficit of more than 4 percent of GDP in 2015, above the EU ceiling of three percent.
Deep divisions have emerged in Brussels over how to handle Paris and Rome's failure to bring their books in order, with Berlin preaching fiscal discipline and leading the call for the two to meet their commitments.
Germany's Commissioner Günther Oettinger wrote an article last month in which he criticised France for breaking the rules.
"It would not be credible to extend the deadline without asking for very clear, concrete steps in return," said Oettinger, who is a close ally of Merkel.